The rapid rise of mobile devices has fueled interest in wireless power transfer, in which wireless power transfer base stations are enabled to wirelessly charge mobile devices. In a typical wireless power transfer system, a base station may have a power supply that includes a magnetic inductive coil acting as a wireless power transmitter, and a mobile device may be configured with a wireless power receiver that includes another magnetic inductive coil. The inductive coil in the receiver may be inductively charged by the inductive coil in the wireless power transmitter. The wireless power receiver may be configured to use the charge transfer to charge an internal battery. In this way, the mobile device may charge itself wirelessly from the base station without the need for any hard-wire connection to a power source.